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Long-term measurements of mass and elemental dry deposition (Mg,

ABSTRACT. Long-term dry deposition and dichotomous coarse particle samples were collected between November 1993 and October 1995 in Chicago, IL, as part of ( ) the Lake Michigan Mass Balance Study LMMBS . In addition, short-term dry ( ) deposition and airborne coarse particle Noll Rotary Impactor samples were collected during the Atmospheric Exch ange Over Lakes and Oceans Study ( ) AEOLOS . These samples were an alyzed for trace metals an d modeled using the ( ) ( ) U.S. EPA's Chemical Mass Balance CMB Model Version 7 to determine the sources of these particles. The modeled source contributions were similar. The results indicate that light duty unleaded vehicles, soil dust, and heavy duty diesel vehicles were the major sources of ambient coarse and dry deposited particles in Ch icago. The other sources found were lime kilns, coke dust, aluminum foundryreverberatory furnace, coal-® red power plant, paint spray booth, and municipal incineration. The results from this study indicate that the CMB approach can be used to determine the source of deposited particles.

Recently, greased surrogate surfaces h ave been successfully used to ( ) directly measure the dry deposition of semivolatile organic chemicals SVOCs . However, it has been dif® cult to interpret these measurements because the extent to which the grease used to collect the deposited particles absorbs the gas phase SVOCs is not clear. In this study, the partitioning between polycyclic aromatic ( ) hydrocarbons PAHs in the vapor phase and grease used on surrogate surfaces was investigated. This interaction was parameterized by de® ning a partition factor as the ratio between the individual PAH air phase equilibrium concentration and the PAH grease ph ase equilibrium concentration multiplied by the square root of the PAH diffusion coef® cient in the grease. This factor was used to estimate the vapor phase PAH deposition to greased surrogate surfaces deployed in the ® eld for periods between 1 and 5 days. For these samples, naphthalene h ad the largest gas phase deposition to the grease while¯uorene had the lowest. Th e amount of deposited PAH attributable to gas phase deposition was not signi® cant compared to particle deposition. Th e air r r r r r grease partition factor was found to be correlatedto its octanol r r r r r air partition coef® cient r ) 77% .